Method for manufacturing a sensor device with a buried deep trench structure and sensor device

ABSTRACT

A sensor device includes: a semiconductor substrate having a sensing region which extends vertically below a main surface region of the semiconductor substrate into the substrate; a semiconductor capping layer that extends vertically below the main surface region into the substrate; a buried deep trench structure that extends vertically below the capping layer into the substrate and laterally relative to the sensing region, the buried deep trench structure including a doped semiconductor layer that extends from a surface region of the buried deep trench structure into the substrate; a trench doping region that extends from the doped semiconductor layer of the buried deep trench structure into the substrate; and electronic circuitry for the sensing region in a capping region of the substrate vertically above the buried deep trench structure. Methods of manufacturing the sensor device are also provided.

TECHNICAL FIELD

Embodiments of the present disclosure relate to the field ofmanufacturing sensor devices in a semiconductor substrate. Morespecifically, embodiments relate to the field of manufacturing sensordevices with a buried deep trench structure, being particularlybeneficial in the field of optical sensor devices, such as image sensorarrays or time of flight sensors, by providing a crosstalk preventionand drift field generation.

BACKGROUND

Photosensitive components have become an indispensable part of thesemiconductor market. These chips, such as optical sensors, are becomingsmaller and have to achieve the required luminous efficacy even with asignificantly reduced surface area. For image sensor arrays it is veryimportant to suppress crosstalk between the individual pixels of thearray, in particular for small pixels or in the case of high pixeldensities. Therefore, deep trenches can be used to prevent optical andelectrical crosstalk between the pixels. Deep trenches can be processedfrom the wafer front side, for example a front side of a semiconductorsubstrate, with the drawback of surface area consumption. Alternatively,trenches can be processed from the backside of the semiconductorsubstrate, resulting in a more cost intensive process

Furthermore, for example in time of flight sensor devices, electricaldrift fields are needed to accelerate generated charge carriers, forexample electrons or holes. This can be done by special arrangements ofdoping profiles, leading to cost intensive process sequences. The dopingprofiles may be introduced into the semiconductor substrate by asequence of epitaxial depositions, ion implantations and temperatureprocesses. These processes are complicated, expensive and littlereproducible.

Therefore, there is a need for a new method for efficientlymanufacturing sensor devices having an effective crosstalk preventionand drift field generation.

Such a method is provided by the method for manufacturing a sensordevice with a buried deep trench structure according to claim 1. Inaddition, specific implementations of different embodiments of themethod for manufacturing a sensor device are defined in the dependentclaims.

SUMMARY

According to an embodiment, a method for manufacturing a sensor devicewith a buried deep trench structure comprises: providing a semiconductorsubstrate having a sensing region, which extends vertically below a mainsurface region of the semiconductor substrate into the semiconductorsubstrate, wherein a masking layer is arranged on the main surfaceregion of the semiconductor substrate; etching a deep trench structureinto the semiconductor substrate through revealed areas of the maskinglayer for arranging the deep trench structure laterally relative to thesensing region and vertically from the main surface region into thesemiconductor substrate; selectively depositing by epitaxy a dopedsemiconductor layer on a surface region of the deep trench structure forproviding a coated deep trench structure; at least partially removingthe masking layer for revealing the main surface region of thesemiconductor substrate; depositing a semiconductor capping layer on themain surface region of the semiconductor substrate, wherein thesemiconductor capping layer covers and closes the coated deep trenchstructure and forms together with the semiconductor substrate athickened semiconductor substrate having the buried deep trenchstructure; and out-diffusing dopants of the doped semiconductor layerinto the thickened semiconductor substrate wherein the out-diffuseddopants provide a trench doping region that extends from the dopedsemiconductor layer into the semiconductor substrate.

According to a further embodiment, a sensor device with a buried deeptrench structure comprises: a semiconductor substrate having a sensingregion, which extends vertically below a main surface region of thesemiconductor substrate into the semiconductor substrate; asemiconductor capping layer that extends vertically below the mainsurface region of the semiconductor substrate into the semiconductorsubstrate; a buried deep trench structure that extends vertically belowthe capping layer into the semiconductor substrate and laterallyrelative to the sensing region, wherein the buried deep trench structurecomprises a doped semiconductor layer, the doped semiconductor layerextending from a surface region of the buried deep trench structure intothe semiconductor substrate; a trench doping region that extends fromthe doped semiconductor layer of the buried deep trench structure intothe semiconductor substrate; electronic circuitry for the sensing regionin a capping region of the thickened semiconductor substrate verticallyabove the buried deep trench structure.

Those skilled in the art will recognize additional features andadvantages upon reading the following detailed description, and uponviewing the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the method for manufacturing a sensor device with aburied deep trench structure are described herein making reference tothe appended drawings and figures.

FIG. 1 shows an exemplary process flow (flowchart) of a method formanufacturing a sensor device with a buried trench structure accordingto an embodiment.

FIGS. 2 a-g show schematic cross-sectional views (schematic snapshots)of a semiconductor substrate and manufactured elements of the sensordevice at different stages of the manufacturing method according to anembodiment.

FIGS. 3 a-d show schematic top views of a semiconductor substrate andmanufactured elements of the sensor device at different stages of themanufacturing method according to an embodiment.

FIGS. 4 a-f show schematic top views of semiconductor substrates andmanufactured elements of the sensor device according to furtherembodiments.

FIG. 5 shows a schematic cross-sectional view of a semiconductorsubstrate and manufactured elements of a sensor device according to anembodiment.

FIG. 6 shows schematic cross-sectional views (schematic snapshots) of asemiconductor substrate and elements of the manufactured sensor atdifferent stages of the manufacturing according to a further embodiment.

FIGS. 7 a-e show cross-sectional electron microscopy images of asemiconductor substrate at different stages of the manufacturing methodaccording to an embodiment.

FIG. 8 shows a lateral distribution of dopants of a trench doping regionof a sensor device according to an embodiment of the manufacturingmethod.

FIG. 9 shows schematic cross-sectional views (schematic snapshots) of asemiconductor substrate and elements of the sensor device at differentstages of the manufacturing according to a further embodiment.

FIG. 10 shows schematic cross-sectional views (schematic snapshots) of asemiconductor substrate and elements of the sensor device at differentstages of the manufacturing according to a further embodiment.

FIG. 11 shows schematic cross-sectional views (schematic snapshots) of asemiconductor substrate and elements of the sensor device at differentstages of the manufacturing according to a further embodiment.

FIG. 12 shows a schematic cross-sectional view of a sensor device with aburied deep trench structure according to an embodiment.

DETAILED DESCRIPTION

Before discussing the present embodiments in further detail using thedrawings, it is pointed out that in the figures and the specificationidentical elements and elements having the same functionality and/or thesame technical or physical effect are usually provided with the samereference numbers or are identified with the same name, so that thedescription of these elements and of the functionality thereof asillustrated in the different embodiments are mutually exchangeable ormay be applied to one another in the different embodiments.

In the following description, embodiments are discussed in detail,however, it should be appreciated that the embodiments provide manyapplicable concepts that can be embodied in a wide variety ofsemiconductor devices. The specific embodiments discussed are merelyillustrative of specific ways to make and use the present concept, anddo not limit the scope of the embodiments. In the following descriptionof embodiments, the same or similar elements having the same functionhave associated therewith the same reference signs or the same name, anda description of such elements will not be repeated for everyembodiment. Moreover, features of the different embodiments describedhereinafter may be combined with each other, unless specifically notedotherwise.

It is understood that when an element is referred to as being“connected” or “coupled” to another element, it may be directlyconnected or coupled to the other element, or intermediate elements maybe present. Conversely, when an element is referred to as being“directly” connected to another element, “connected” or “coupled,” thereare no intermediate elements. Other terms used to describe therelationship between elements should be construed in a similar fashion(e.g., “between” versus “directly between”, “adjacent” versus “directlyadjacent”, and “on” versus “directly on”, etc.).

For facilitating the description of the different embodiments, thefigures comprise a Cartesian coordinate system x, y, z, wherein thex-y-plane corresponds, i.e. is parallel, to the main surface region ofthe semiconductor substrate, and wherein the depth direction vertical tothe main surface region and into the semiconductor substrate correspondsto the “z” direction, i.e. is parallel to the z direction. In thefollowing description, the term “lateral” means a direction parallel tothe x-direction, wherein the term “vertical” means a direction parallelto the z-direction.

The terms “above” or “vertically above” or “top” refer to a relativeposition located in the vertical direction which extends from the mainsurface region of the semiconductor substrate and points away from thesemiconductor substrate. Similarly, the terms “below” or “verticallybelow” or “bottom” refer to a relative position located in the verticaldirection which extends from the main surface region of thesemiconductor substrate and points into the semiconductor substrate.

FIG. 1 and FIGS. 2 a-g show an exemplary process flow or flowchart of amethod 100 of manufacturing a sensor device with a buried trenchstructure according to an embodiment. In order to facilitate thepresentation, the description of FIG. 1 already includes referencenumbers of the embodiment shown in FIGS. 2 a-g . The references numbersrelating to FIGS. 2 a-g are represented by two-digit numbers.

As shown in FIG. 1 , the method 100 comprises a step 110 of providing asemiconductor substrate 10, referred to as substrate 10 hereafter forthe sake of clarity. The substrate 10 has a sensing region 14, whichextends vertically below a main surface region 12 of the substrate 10into the substrate 10, wherein a masking layer 16 is arranged on themain surface region 12 of the substrate 10. In step 120, a deep trenchstructure 20 is etched into the substrate 10 through revealed areas 18of the masking layer 16. The deep trench structure 20 extends verticallyfrom the main surface region 12 into the substrate 10 and is arrangedlaterally relative to the sensing region 14. The deep trench structure20 may border the sensing region 14 directly, or may be at a distancefrom the sensing region 14. In step 130, a doped semiconductor layer 32,referred to as doped layer 32 in the following, is selectively depositedby epitaxy on a surface region 22 of the deep trench structure 20 forproviding a coated deep trench structure 30. The doped layer 32 may havea defined thickness and a defined doping concentration. The maskinglayer 16 prevents the main surface region 12 from being covered withdopants during the selective epitaxial deposition 130. In step 140, themasking layer 16 is at least partially removed for revealing the mainsurface region 12 of the substrate 10. In step 150, a semiconductorcapping layer 52, referred to as capping layer 52 hereafter, isdeposited on the main surface region 12 of the substrate 10 to cover andclose the coated deep trench structure 30. The capping layer 52 formstogether with the substrate 10 a thickened semiconductor substrate 10′,referred to as thickened substrate 10′ in the following. The thickenedsubstrate 10′ has the coated deep trench structure 30 buried therein,i.e. has the buried deep trench structure 50. The buried deep trenchstructure 50 may be configured to form a barrier to optical andelectronic signals. In step 160, dopants of the doped layer 32 areout-diffused into the thickened substrate 10′, the out-diffused dopantsproviding a trench doping region 60 that extends from the doped layer 32into the thickened substrate 10′.

Thus, embodiments describe a process for manufacturing a sensor devicewith a buried deep trench structure 50, so that the buried deep trenchstructure 50 may be etched from a front side of a wafer. The etching 120of the deep trench structure 20 from the main surface region 12 providesan efficient way to arrange the deep trench structure 20 close by thesensing region 14 which also extends vertically below the main surfaceregion 12. Still, after burying the deep trench structure, the mainsurface region 12′, including regions vertically above the buried deeptrench structure 50, is available to be used in the further processsteps. This efficiently solves the problem of surface consumption ofdeep trench structures in sensor devices. In other words, trenches maybe etched from the front side, what is an established process, butwithout any front side area consumption due to an overgrowth, forexample with silicon epitaxy. The avoidance of surface area consumptionby the deep trenches may be beneficial for a further process flow. Forexample, electronic circuitry, such as readout circuitry, may bearranged, e.g. placed or manufactured directly, on the main surfaceregion 12′ vertically above the buried deep trench structure 50, forexample readout circuitry of pixels on the surface, for example of pixeldevices forming a part of a sensor device. At the same time, maximizingthe amount of available surface area is favorable to the luminousefficacy of an optical sensor. In other words, the presented disclosureuses deep trenches, for example empty deep trenches, with a dopingprofile and solves the space problem. After closing the deep trenches,an arbitrary semiconductor process flow may be carried out to furtherprocess the obtained substrate 10′. The trenches, e.g. of the burieddeep trench structure, are closed at the top but may be still empty inthe depth, what may give a good characteristic for an optical componentof a crosstalk behavior of the sensor device to be manufactured.

For example, the sensing region 14 and a neighboring sensing regionwithin the substrate each form a part of different pixel devices of asensor device. The deep trench structure may prevent optical and/orelectronic crosstalk between the different pixel devices. That is, thedeep trench structure 20 may attenuate or prohibit a transfer of anelectronic or an optical signal out of the sensing region 14 and/or mayattenuate or prohibit a transfer of an electronic or an optical signalinto a neighboring region of the substrate, for example a neighboringfurther sensing region. For example, an electromagnetic signal to bedetected in the sensing region 14 may be reflected at the interfacebetween the substrate 10 and the deep trench structure 50. Thus, theelectromagnetic signal may remain within the sensing region 14, thusincreasing the probability of the electromagnetic signal to be detectedin the sensing region 14. Further, due to the reflection of theelectromagnetic signal, the electromagnetic signal may be prevented fromentering neighboring regions of the substrate. For example, theelectromagnetic signal may be prevented from entering a neighboringsensing region, preventing an erroneous or undesirable detection of theelectromagnetic signal in another sensing region than the sensing region14. For example, the reflection of an electromagnetic signal at theinterface between the substrate 10 and the deep trench structure 50 mayoccur due to total internal reflection, such that the electromagneticsignal may be reflected entirely or almost entirely. Further, the deeptrench structure 20 may hinder charge carries to move into neighboringregions of the substrate 10. Thus, the deep trench structure 20increases the probability that a charge carrier is detected within thesensing region 14 within which the charge carrier was generated byconversion of an electromagnetic signal. Thus, the deep trench structure20 may prevent the charge carrier to be detected erroneously orundesirably in another sensing region than the sensing region 14. Thus,the deep trench structure 20 may increase the yield of anelectromagnetic signal entering into the sensing region 14 through aregion of the main surface region 12 vertically above the sensing region14 to be detected in the sensing region 14.

By depositing the doped layer 32 on the surface region 22, such aswalls, of the deep trench structure 30, tunable doping profiles fordrift field generation can be created in the sensing region 14. Based onthe out-diffusing 160 of dopants of the doped layer 32 into thethickened substrate 10′, the resulting doping profile can be tuned toprovide electric drift fields in the substrate 10′ and/or in the sensingregion 14, 14′. Thus, the method 100 allows a very preciselyreproducible generation of doping profiles with a low complexity processsequence by using a selective epitaxial deposition, for example a highdoped selective silicon epitaxy deposition on the trenches, for exampleon the sidewall of the trenches, and by controlling a doping profilewith an annealing process, such as a temperature process.

Thus, the proposed method 100 is an effective method on the way to smallpixels, for example small pixels with high resolution which may be partof a sensor device.

In the following, referring to FIGS. 2 a-g an exemplary embodiment ofthe process flow of the method 100 is described. FIGS. 2 a-g showschematic cross-sectional views of the substrate along a vertical plane.FIGS. 2 a-g show the (at the respective process stage) manufacturedelements at several process stages of the method 100 for manufacturingthe sensor device.

FIG. 2 a —Provided substrate: FIG. 2 a shows an exemplary embodiment ofthe substrate 10 as provided in step 110 of method 100. The substrate 10may have a rectangular cross-section along a vertical axis (i.e. in thedepth direction or z direction). The substrate 10 may comprise silicon,germanium or any other semiconductor material. The substrate 10 maycomprise a bulk or epitaxially (EPI) grown semiconductor material. Thesubstrate 10 may comprise dopants with a doping concentration and adoping type being either n-type or p-type.

The main surface region 12 may be a planar surface and may form a topsurface of the substrate 10. The vertical dimension of the sensingregion 14 may cover the complete vertical dimension of the substrate 10,or only part of it. The sensing region 14 has a lateral dimension, whichmay be smaller than the lateral dimension of the substrate 10.

According to an embodiment, the sensing region 14 forms a conversionregion of an optical sensor to be manufactured, wherein the conversionregion converts an electromagnetic signal into photo-generated chargecarriers. A sensing region 14 of such an optical sensor may form part ofa device known as pixel, which may comprise further components, e.g.processing circuitry. This pixel itself may form part of atwo-dimensional integrated pixel array for receiving electromagneticradiation, for example optical visible or infrared radiation, whereinthe respective pixels provide an electrical output signal according to aparameter to be measured by the optical sensor. The optical sensor mayfor example be an imaging array or a time of flight sensor.

The revealed areas 18 of the masking layer 16 expose the main surfaceregion 12 of the substrate 10. The lateral structure (i.e. the lateraldimension and the lateral form) of the revealed areas 18 of the maskinglayer 16 provide a lateral structure for a deep trench structure formedin following process steps. The revealed areas 18 of the masking layer16 may have been formed by partially removing the masking layer 16. Thispartial removal of the masking layer 16 may have been performed by alithographic process.

FIG. 2 b —trench etching: In step 120 of the method 100, parts of thesubstrate 10 are removed by etching, starting from the revealed areas 18of the masking layer 16 and etching into the substrate 10 to form thedeep trench structure 20, as shown in FIG. 2 b . During the etchingprocess 120, the masking layer 16 may be partially removed. The trenchetching process 120 is configured to remove material of the substrate 10at a faster rate than material of the masking layer 16.

After step 120, the substrate 10 comprises the deep trench structure 20.The lateral structure of the deep trench structure 20 emanates from thelateral structure of the revealed areas 18 of the masking layer 16.

The deep trench structure may have a depth 27. The depth 27 of the deeptrench structure 20 may be a vertical dimension of the deep trenchstructure 20.

According to an embodiment, the depth 27 may be in the range between 1μm and 100 μm, or in another embodiment, in the range between 2 μm and20 μm.

The deep trench structure 20 comprises a surface region 22. The surfaceregion 22 of the deep trench structure 20 may be a boundary between thedeep trench structure 20 and the substrate 10. The surface region 22 ofthe deep trench structure 20 may comprise a wall 24, which may be aboundary that confines the deep trench structure 20 in a lateraldirection. The surface region 22 of the deep trench structure 20 mayalso comprise a bottom 26, which may be a boundary that confines thedeep trench structure 20 in the vertical direction.

The deep trench structure 20 has a width 25. This width 25 may be alateral distance between two immediately opposing walls 24, or a lateraldistance between two opposite regions of the surface region 22, thelateral distance being measured perpendicular to a longitudinaldirection of a trench or a trench portion of the deep trench structure25.

According to an embodiment, the width 25 is large enough that anevanescent wave of a total internal reflection of an electromagneticsignal at the interface between the substrate 10 and the deep trenchstructure 20 may be hindered to interact with neighboring regions of thesubstrate 10. Thus, the reflection may be a frustrated total internalreflection.

According to an embodiment, the width 25 is larger than a fewwavelengths of the electromagnetic signal to be detected, such that thereflection of an electromagnetic signal at the interface between thesubstrate 10 and the deep trench structure 20 may be a frustrated totalinternal reflection.

A trench aspect ratio of the deep trench structure 20 may be defined asa ratio of the trench height 27 and the width 25. According to anembodiment, the trench aspect ratio of the deep trench structure 20 isin a range between 1 and 100 or between 5 and 60.

The trench etching process 120 may have different etching rates fordifferent etching directions regarding substrate 10. For example, thetrench etching process 120 may primarily etch a vertical surface of thesubstrate 10. Thus, deep trench structures 20 with a high trench aspectratio may be etched by the trench etching process 120.

The deep trench structure 20 is arranged laterally relative to thesensing region 14 of the substrate 10. The deep trench structure 20 doesnot necessarily adjoin the sensing region 14, but may also be spacedapart from the sensing region 14 by a region of the substrate 10 whichis not part of the sensing region 14.

The deep trench structure 20 may surround, e.g. enclose entirely or onlypartly the sensing region 14. Optionally, thus, the deep trenchstructure 20 may enclose the sensing region 14 entirely.

According to an embodiment, the deep trench structure 20 may comprisedeep trench portions (not shown in FIGS. 2 a-g , see in FIG. 3 a forexample) which may be arranged to laterally confine the sensing region14. In such a case, the above described properties of the deep trenchstructure 20 apply equally to the individual deep trench portions andthe arrangement of the plurality of deep trench portions forms the deeptrench structure 50.

FIG. 2 c —doped EPI deposition: In step 130 of the method 100, a dopedlayer 32 is deposited on the surface region 22 of the deep trenchstructure 20 by a selective epitaxy (EPI) deposition, as shown in FIG. 2c . The doped layer 32 and the deep trench structure 20 form a coateddeep trench structure 30.

The selective epitaxial deposition is configured to selectively deposita doped semiconductor material primarily on the surface region 22 of thedeep trench structure 20.

The deposition of the doped layer 32 on the surface of the deep trenchstructure 20 is an efficient way to introduce a doping concentration ora doping profile in the substrate. Very reproducible results can beobtained with the control of the thickness and the doping concentrationof the doped layer 32.

The selective epitaxial deposition may comprise exposing the substrate10 to one or more of the following gases: dichlorosilane, HCl, B₂H₂, andH₂. The selective epitaxial deposition may be performed at a temperaturebetween 600° C. and 1000° C., for example at a temperature around 760°C. The selective epitaxial deposition may be configured to achieve aspecific doping concentration of the doped layer 32.

During the selective epitaxial deposition of the doped layer 32, themain surface region 12 of the substrate 10 is still covered by themasking layer 16 to prevent the doped layer 32 from forming thereon.

The doped layer 32 may cover the entire surface region 22 of the deeptrench structure 20. The doped layer 32 may comprise a thickness 34. Thethickness 34 of the doped layer 32 may be a distance between a surfaceregion 36 of the doped layer 32 and a surface region 22 of the deeptrench structure 20. The surface region 36 of the doped layer 32 may bea boundary between the coated deep trench structure 30 and the dopedlayer 32. The thickness 34 of the doped layer 32 may be in a rangebetween 1 nm and 1 μm.

The doped layer 32 may comprise a semiconducting material, for examplesilicon. A doping type of the doped layer 32 may be n-type or p-type. Adoping concentration of the doped layer 32 may be in a range between10¹⁶ cm⁻³ and 10²⁰ cm⁻³.

According to an embodiment, the doping inside the trenches, that is thedeposition of the doped layer 32, is done with a selective high dopedsilicon epitaxial deposition with the masking layer 16, which may be acapping layer, on the main surface region 12.

According to an embodiment, the material deposited by the selectiveepitaxial deposition is primarily in the deep trench structure 20 andnot on the main surface region 12 of the substrate 10.

According to an embodiment, the doped layer 32 is deposited on thetrench wall by a selective epitaxial deposition and the doped layer 32is a thin layer and has a high doping concentration. Thus, the width 25remains almost unaltered after deposition of the doped layer 32, so thatthe deep trench structure 20 keeps its beneficial properties regardingcrosstalk prevention, and at the same time, an efficient drift fieldgeneration is granted.

FIG. 2 d —pad etching: In step 140 of the method 100, the masking layer16 is at least partially removed for revealing the main surface region12 of the substrate 10. The removing 140 of the masking layer 16 maycomprise an etching process, wherein the etching process is adapted toetch primarily the masking layer 16 and to etch less efficiently or notat all the substrate 10. The removing 140 of the masking layer 16 may beapplied to the entire masking layer 16 or only to parts of the maskinglayer 16, referring to a lateral dimension of the masking layer 16. Theremoving 140 of the masking layer 16 removes at least parts of themasking layer 16 in its entire vertical dimension, so that theunderlying main surface region 12 of the substrate 10 is exposed. Thus,the removing 140 of the masking layer 16 at least partially exposes themain surface region 12 of the substrate 10.

According to an embodiment, the removing 140 of the masking layer 16exposes those parts of the main surface region 12 of the substrate 10,which are arranged adjacent to the coated deep trench structure 30.

According to a further embodiment, the removing 140 of the masking layer16 exposes the entire main surface region 12 of the substrate 10.

After step 140, the main surface region 12 of the substrate 10 is atleast partially exposed as shown in FIG. 2 d.

After step 140 and before step 150, the method 100 may optionallycomprise filling the coated deep trench structure 30 with a gas or witha dielectric material. The optional gas or dielectric material fillingthe coated deep trench structure 30 may be a material which is opaquefor an optical radiation, in particular for an optical radiation to bedetected in the sensing region 14. In other words, the gas or thedielectric material filling the coated deep trench structure 30 may beadapted to absorb or attenuate optical radiation, i.e. electromagneticradiation, or may be chosen so that the optical radiation is refractedat least partially to not pass through the material. Alternatively, theoptional gas or dielectric material filling the coated deep trenchstructure 30 may have a dielectric function adapted to achieve a totalinternal reflection or a frustrated total internal reflection of anelectromagnetic signal at an interface between the coated deep trenchstructure 30 and the substrate 10.

FIG. 2 e : capping layer deposition: In step 150 of method 100, thecapping layer 52 is deposited on the main surface region 12, as shown inFIG. 2 e . The capping layer 52 is also deposited adjacent to the coateddeep trench structure 30, more specifically in a region locatedvertically above the coated deep trench structure 30. Thus, the cappinglayer 52 covers and closes the coated deep trench structure 30, which isthus buried in the substrate 10 during step 150. The deposition 150 ofthe capping layer 52 may comprise an epitaxial (EPI) process, such as anepitaxial (EPI) overgrow. In one embodiment, the deposition of thesemiconducting capping layer 52 comprises an epitaxial (EPI) overgrowprocess at atmospheric pressure.

The capping layer 52 may comprise silicon, germanium or any othersemiconducting material. In one embodiment, the capping layer 52 has thesame material as the substrate 10. The capping layer 52 may comprise adoping concentration and a doping type, which may be n-type or p-type.The doping type of the capping layer 52 may have the same or a differentdoping type as the substrate 10.

The capping layer 52 and the substrate 10 form a thickened substrate 10′comprising a surface region 12′, which may form a top surface of thethickened substrate 10′.

The capping layer 52 has a thickness 54, which may be a verticaldistance between the surface region 12′ of the thickened substrate 10′and the main surface region 12 of the substrate 10. In other words, thethickness 54 may be a depth of the capping layer 52. Thus, the thickness54 may also be a depth of the buried deep trench structure 50 below themain surface region 12′ of the thickened substrate 10′. The cappinglayer 52 may cover the main surface region 12 of the substrate 10partially or completely. The capping layer 52 may comprise a region,which extends vertically above the sensing region 14 into the cappinglayer 52, and which may extend the sensing region 14 to form togetherwith it a sensing region 14′. The sensing region 14′ extends verticallybelow the main surface region 12′ into the thickened substrate 10′.

The depth of bury 54, that is the thickness of the capping layer 52, mayhave a chosen value. A thin value of the depth of bury 54 may improvethe crosstalk suppression of the buried deep trench structure 50. Athick value of the depth of bury 54 may provide more space forprocessing electronic circuitry vertically above the buried deep trenchstructure 50.

According to an embodiment, the thickness 54 of the capping layer 52 maybe in a range between 100 nm and 10 μm.

According to an embodiment, the buried deep trench structure 50 may beempty or filled with gas or it may be partially filled with a dielectricmaterial or with any other material. In this context, empty may refer toa filling with any gas, for example air or a process gas, or empty mayrefer to a gaseous environment at a pressure lower than ambientpressure. Alternatively, the buried deep trench structure 50 may befilled or partially filled with a solid material, for example adielectric material.

According to an embodiment, the buried deep trench structure 50 isfilled with a process gas of the epitaxial overgrow process.

According to an embodiment, the deposition of the capping layer 52 maycomprise depositing semiconducting material on the surface region 36 ofthe doped layer 32, so that the capping layer 52 may at least partiallycover the doped layer 32.

The buried deep trench structure 50 emanates from the coated deep trenchstructure 30 which itself results from the deep trench structure 20.Thus, properties and functions of the deep trench structure 20 discussedabove equally apply to the buried deep trench structure 50. Propertiesand functions discussed in the context of the interface between the deeptrench structure 20 or the coated deep trench structure 30 and thesubstrate 10 equally apply regarding the interface between the burieddeep trench structure 50 and the substrate 10.

According to an embodiment, and resulting from what is indicated above,the buried deep trench structure 50 may comprise multiple deep trenchportions (not shown in FIG. 2 , shown in FIGS. 3 b-d , FIGS. 4 a-f ,FIG. 5 ) to which, the above described properties of the buried deeptrench structure 50 apply equally.

FIG. 2 f —dopant out-diffusion: In step 160 of method 100, dopants ofthe doped layer 32 are out-diffused into the thickened substrate 10′.The step of out-diffusing may comprise an annealing process, which maybe a temperature process, which may comprise exposing the device withthe substrate 10 to a high temperature. The out-diffusing of dopantscomprises a drift or a movement of dopants from the doped layer 32 intothe thickened substrate 10′. The region, within which the dopants aredistributed forms a trench doping region 60, as shown in FIG. 2 f . Theout-diffusion 160 of dopants establishes a doping profile 74 thatextends from the doped layer 32 into the thickened substrate 10′.

The doping profile 74 describes the local distribution of dopants in thetrench doping region 60. The trench doping region 60 may be laterallyadjacent to the sensing region 14′, but the trench doping region mayalso overlap with the sensing region 14′. The trench doping region 60may also laterally confine the sensing region 14′.

The out-diffusing 160 may be adapted to control the drift or themovement of dopants, such that after the step 160, the trench dopingregion 60 comprises a specific dimension and/or form with a specificdoping profile 74. The doping profile 74 may be changed to reach anoptimum adjustment of the electric fields. A maximum dopingconcentration may be in a range between 10¹⁴ and 10¹⁸ cm⁻³, or between10¹⁵ and 10¹⁷ cm⁻³.

According to an embodiment, the doping profile 74 is configured toefficiently separate charge carriers of opposite charge, such aselectrons and holes, which were generated by converting anelectromagnetic signal into charge carriers.

According to an embodiment, the doping profile 74 is configured tooptimize the path of charge carriers towards an electronic contactconfigured for collecting the charge carrier, so that a readout-speedcan be enhanced.

According to an embodiment, the doping profile 74 is configured toefficiently accelerate charge carriers away from the interface betweenthe buried deep trench structure 50 and the substrate 10′, so that aleakage is reduced. The leakage may for example be a recombination ofcharge carriers at interface between the buried deep trench structure 50and the substrate 10′.

FIG. 2 g —optional electronic circuitry: As shown in FIG. 2 g , in anoptional step 170, an electronic circuitry 70, such as a readoutcircuitry, for the sensing region 14′ may be created at least partiallyvertically above the buried deep trench structure 50. The circuitry mayat least in part be located within a capping region 72 of the thickenedsubstrate 10′, or alternatively, may be located on the top surface ofthe thickened substrate 10′. The creation of the circuitry 70 maycomprise a sequence of process steps, including, for example, one orseveral of depositing a material, removing a material, doping a materialor treating a material chemically or mechanically. During creation ofthe electronic circuitry 70, the thickened substrate 10′ may be changedor affected by a process step.

The capping region 72 extends vertically above the buried deep trenchstructure 50 into the thickened substrate 10′ and to the main surfaceregion 12′ and it may exceed the main surface region 12′ to extendvertically above the main surface region 12′. Creating the electroniccircuitry 70 affects the capping region 72, in particular a part of themain surface region 12′ within the capping region 72. The electroniccircuitry 70 may extend vertically above and/or below the main surfaceregion 12′ of the thickened substrate 10′. The electronic circuitry 70may extend into the capping region 72 and/or into the sensing region14′. The electronic circuitry may also extend into the trench dopingregion 60.

According to an embodiment, the electronic circuitry is arrangedpartially within the thickened substrate 10′. Such an arrangementfacilitates the fabrication of common semiconductor circuitry, forexample doping regions for read-out contacts.

According to an embodiment, the electronic circuitry 70 may comprisecontact regions within the thickened substrate 10′. The contact regionmay for example comprise a higher doping concentration of the samedoping type as the sensing regions 14′ so that charge carriers from thesensing regions 14′-1, 14′-2 may be collected in the contact regions.

According to an embodiment, the electronic circuitry 70 is a readoutcircuitry to collect electronic charges from the sensing region 14′.

According to an embodiment, the sensing region 14′ and the electroniccircuitry 70 form parts of a pixel device which is part of a sensordevice comprising multiple pixel devices. The multiple pixel devices maybe separated from each other by the buried deep trench structure 50.More specifically, an individual pixel device of the multiple pixeldevices may be separated from its neighboring pixel devices by one oremultiple deep trench portions of the buried deep trench structure 50.

According to an embodiment, electronic circuit paths are placed inregions located vertically above the buried deep trench structure.

In the following, a number of different possible implementations of themethod 100 are exemplarily described.

In the present description of embodiments of the method 100, the same orsimilar elements having the same structure and/or function are providedwith the same reference numbers or the same name, wherein a detaileddescription of such elements will not be repeated for every embodiment.Thus, the above description with respect to FIGS. 1 a and 2 a-g isequally applicable to the further embodiments as described below. In thefollowing description, essentially the differences, e.g. additionalelements, to the embodiment as shown in FIG. 1 a and FIGS. 2 a-g and thetechnical effect(s) resulting therefrom are discussed in detail.

FIGS. 3 a-d show schematic top views (schematic snapshots) of substrates10, 10′ and manufactured elements of sensor devices at two differentstages of the method 100 according to embodiments.

FIG. 3 a refers to the step 120 of etching the deep trench structure 20into the substrate 10, as also described in the description of FIG. 2 b.

According to an embodiment, the deep trench structure 20 may comprise aplurality of deep trench portions 20-1, 20-2, . . . , 20-n, e.g. fourdeep trench portions 20-1, 20-2, . . . , 20-4 as shown in FIG. 3 a .Each of the deep trench portions 20-1, 20-2, . . . , 20-n may comprisean individual width and depth. For example, the deep trench portions20-1, 20-2, . . . 20-4 may have a common width 25, which is referred toas the width 25 of the deep trench structure 20. According to theembodiment, the individual deep trench portions 20-1, 20-2, . . . , 20-4may have a common depth, which is referred to as the depth 27 of thedeep trench structure (cf. FIG. 2 b ). A deep trench portion 20-1, 20-2,. . . , 20-n may have a length 21-1, 21-2, . . . , 21-n, which is alongitudinal dimension of the deep trench portion 20-1, 20-2, . . . ,20-n perpendicular to the width 25 of the respective deep trench portion20-1, 20-2, . . . , 20-n. Each deep trench portion 20-1, 20-2, . . .20-n may comprise an individual length 21-1, 21-2, . . . , 21-n. Forexample, as shown in FIG. 3 a , the deep trench portions 20-1, 20-2 maycomprise the lengths 21-1, 21-2. The deep trench portions 20-1, 20-2, .. . 20-n may be arranged to partially or completely laterally surroundthe sensing region 14, as indicated above. For example, as shown in FIG.3 a , the four deep trench portions 20-1, 20-2, . . . 20-4 may partiallysurround the sensing region 14. According to the embodiment, twoneighboring deep trench portions of the deep trench portions 20-1, 20-2,. . . 20-4 are arranged at an angle of 90°, the four deep trenchportions 20-1, 20-2, . . . 20-4 being arranged in a rectangleconfiguration.

According to an embodiment, the deep trench portions 20-1, 20-2, . . .20-n may be arranged in an equiangular polygon configuration, so thattwo of the n deep trench portions 20-1, 20-2, . . . 20-n may be arrangedat an angle of 360°/n.

According to an embodiment, the deep trench portions 20-1, 20-2, . . .20-n may be arranged in arbitrary sequence at arbitrary angles topartially or completely laterally surround the sensing region 14.

The sensing region 14 may have an arbitrary lateral form. The lateraldimension of the sensing region 14 may be defined by one ore multiplelateral sensing region dimensions. For example, according to theembodiment shown in FIG. 3 b , the lateral form of the sensing region 14is rectangular and is defined by two lateral sensing region dimensions15-1, 15-2.

FIGS. 3 b-d refer to step 150 of depositing the capping layer 52 forforming the thickened substrate 10′ having the buried deep trenchstructure 50, as also described in the description of FIG. 2 e.

According to an embodiment, the buried deep trench structure 50 maycomprise a plurality of deep trench portions 50-1, 50-2, . . . , 50-n,which emanate from the deep trench portions 20-1, 20-2, . . . , 20-netched in step 120.

For example, according to the embodiments shown in FIGS. 3 b-c , theburied deep trench structure 50 comprises four deep trench portions50-1, 50-2, . . . , 50-4, which emanate from the deep trench portions20-1, 20-2, . . . , 20-4 etched in step 120 (cf. FIG. 3 a ). The deeptrench portions 50-1, 50-2, . . . , 50-4 may be arranged to partially orcompletely laterally surround the sensing region 14′ which may bedefined by two lateral sensing region dimensions 15-1, 15-2.

FIG. 3 d shows a further embodiment of an arrangement of eight deeptrench portions 50-1, 50-2, . . . , 50-8 which are arranged in anoctagonal arrangement to partially surround a sensing region 14′,wherein the sensing region 14′ may have an octagonal form which may bedefined by a lateral sensing region dimension 15-1.

As shown in FIGS. 3 a-d , the sensing region 14, 14′ does notnecessarily extend over the entire lateral region between individualdeep trench portions 20-1, 20-2, . . . , 20-n, 50-1, 50-2, . . . , 50-n.Thus, the sensing region 14, 14′ does not necessarily adjoin the deeptrench structure 20 or the buried deep trench structure 50.

According to an embodiment, the sensing region 14′ may have an arbitraryform.

According to embodiments, for example embodiments shown in FIGS. 3 b-d ,an electronic circuitry 70, such as a readout circuitry, may be createdfor a sensing region 14′ at least partially vertically above the burieddeep trench structure 50, as described in the description of FIG. 2 g.

FIGS. 4 a-f show schematic top views of substrates 10′ and manufacturedelements of sensors device according to different embodiments.

According to the embodiments, the thickened substrate 10′ comprises aplurality of sensing regions 14′-1, 14′-2, . . . , 14′-n and the burieddeep trench structure 50 comprises a plurality of deep trench portions50-1, 50-2, . . . , 50-n. The deep trench portions 50-1, 50-2, . . .50-n may be arranged to partially (FIGS. 4 a-c, 4 e ) or completely(FIGS. 4 d, 4 f ) laterally surround multiple sensing regions 14′-1,14′-2, . . . , 14′-n individually, i.e. each of multiple parts of theplurality of deep trench portions 50-1, 50-2, . . . , 50-n may bearranged to at least partially surround one of the single sensingregions 14′-1, 14′-2, . . . , 14′-n, respectively. For example, in theexemplary arrangements shown in FIGS. 4 a-c , the deep trench portions50-1, 50-2, . . . , 50-4 partially enclose the sensing region 14′-4.

According to an embodiment, for example the embodiment shown in FIG. 4 d, the deep trench portions 50-1, 50-2, . . . , 50-8 are arranged tocompletely laterally surround multiple sensing regions 14′-1, 14′-2individually.

According to an embodiment, for example the embodiment shown in FIG. 4 f, the deep trench portions 50-1, 50-2, . . . 50-8 are arranged tocompletely laterally surround the sensing region 14′-2 individually.

According to an embodiment, a plurality of deep trench portions 50-1,50-2, . . . 50-n may be arranged to separate individual sensing regions14′-1, 14′-2, . . . 14′-n from each other.

According to an embodiment, a plurality of sensing regions 14′-1, 14′-2,. . . 14′-n may be arranged in an array.

According to an embodiment, each of a plurality of sensing regions14′-1, 14′-2, . . . 14′-n forms a part of an individual pixel device,the individual pixel devices being part of an imaging array or a sensorarray.

FIG. 5 shows a schematic cross-sectional view of an exemplary embodimentof a thickened substrate 10′ and elements of a sensor devicemanufactured by the method 100 according to an embodiment. The thickenedsubstrate 10′ comprises sensing regions 14′-1, 14′-2 to convert anelectromagnetic signal S1 into charge carriers, i.e. into electrons andholes. The thickened substrate 10′ comprises the buried deep trenchstructure 50 comprising deep trench portions 50-1, 50-2, 50-3 which arearranged to separate the neighboring sensing regions 14′-1, 14′-2. Thedeep trench portions 50-1, 50-2, 50-3 are surrounded by the trenchdoping region 60. The trench doping region 60 comprises a doping profilewhich may be optimized to accelerate charge carriers away from theinterface between the buried deep trench portions 50-1, 50-2, 50-3,efficiently reducing leakage or noise of the manufactured sensor deviceduring operation.

The electronic circuitry 70 is partially arranged vertically above thedeep trench portions 50-1, 50-2, 50-3 so that the buried deep trenchstructure 50 does not consume surface area.

According to an embodiment, additional readout circuitry 502 is arrangedon a main surface region 12′ of the thickened substrate 10′ verticallyabove the sensing regions 14′. The additional readout circuitry 502 maybe adapted to perform time of flight measurements.

According to an embodiment, the thickened substrate 10′ comprises aburied doping region 501 which extends vertically below the sensingregions 14′-1, 14′-2 into the substrate 10′. In an embodiment, theburied doping region 501 extends vertically below the sensing regions14′-1, 14′-2 to an opposite surface region 503 of the thickenedsubstrate 10′ opposite to the main surface region 12′.

According to an embodiment, the buried doping region 501 comprises anopposite doping type compared to the sensing region 14, i.e. the burieddoping region 501 may comprise a p-type doping and the sensing region 14may comprise a n-type doping or vice versa. Such an embodiment may bebeneficial for efficiently separating electrons and holes.

According to an embodiment, the trench doping region 60 comprises thesame doping type as the buried doping region 501 of the substrate 10, sothat a specific kind of charge carriers is efficiently acceleratedtowards the main surface region 12′ or an electronic circuitry 70.

According to an embodiment, the trench doping region 60 comprises ahigher doping concentration than the buried doping region 501.

According to an embodiment, the trench doping region 60 and the burieddoping region 501 are p-doped and the sensing region is n-doped, theembodiment being beneficial for an efficient drift of electrons towardsthe main surface area 12 of the substrate and in particular for anefficient drift of electrons towards the electronic circuitry 70 and/orthe additional readout circuitry 502.

In an embodiment, the etching 120 of the deep trench structure 20 maycomprise arranging the deep trench structure 20 vertically from the mainsurface region 12 into the substrate 10 and into a buried doping region501 of the substrate 10.

According to an embodiment, the doped layer 32 (see for example FIGS. 2c-g ) may comprise the same doping type as the buried doping region 501of the substrate 10.

According to an embodiment, the doped layer 32 (see for example FIGS. 2c-g ) further comprises a higher doping concentration than the burieddoping region 501.

According to an embodiment, the doped layer 32 (see for example FIGS. 2c-g ) and the buried doping region 501 are p-doped and the sensingregion is n-doped.

FIG. 6 shows schematic cross-sectional views (schematic snapshots) of asubstrate 10 and manufactured elements of a sensor device at differentstages of the method 100 according to a further embodiment. FIG. 6refers to the optional steps 105 and 106 and the steps 110 and 120 of anembodiment of the method 100. Equal elements shown in different panelsof the figure should be referred to with the same references if notindicated otherwise.

The optional step 105 may be part of the step 110. In step 105, thesubstrate 10 is provided with the sensing region 14, and with themasking layer 16 arranged on the main surface region 12. In the shownembodiment, the masking layer 16 comprises a pad layer 16-1 arrangedadjacent to or on top of the main surface region 12. According to anembodiment, the pad layer 16-1 may be a silicon nitride layer. In theshown embodiment, the masking layer 16 further comprises a hard masklayer 16-2 arranged adjacent to or on top of the pad layer 16-1. Thehard mask layer 16-2 may comprise a composition of materials, which isless sensitive to a specific etch process than a composition of materialof the substrate 10. Thus, an etch process may be configured to removematerial of the substrate 10 at a faster rate than material from thehard mask layer 16-2. In the shown embodiment, a resist layer 601 isarranged on top of the hard mask layer 16-2. The resist layer 601comprises a revealed resist region 602 which exposes a top surfaceregion 603 of the hard mask layer 16-2, as shown in the left panel ofFIG. 6 . For the providing 110 of the substrate 10, in this embodiment,the method 100 comprises an additional step 106 of etching revealedareas 18 into the masking layer 16 through the revealed resist region602 of the resist layer 601. Thus, the lateral structure of the revealedareas 18 of the masking layer 16 emanate from the revealed region 602 ofthe resist layer 601. The step 106 of etching the masking layer 16 maybe followed by or may comprise removing the resist layer 601, so as toprovide the substrate 10 with the masking layer 16 comprising therevealed areas 18, as shown in the center panel of FIG. 6 . The rightpanel of FIG. 6 shows the result of the etching 120 of the deep trenchstructure 20.

According to an embodiment, the optional pad layer 16-1 has a thickness,which is a vertical dimension, in the range between 1 nm and 10 μm or inanother embodiment in the range between 10 nm and 1 μm.

According to an embodiment, the masking layer 16 comprises a pad layer16-1 and a hard mask layer 16-2, wherein the hard mask layer 16-2 isconfigured to be less sensitive to a trench etch process than thesubstrate 10, so that the trench etch process primarily affects regionsof the substrate 10 which are not covered with the masking layer 16.

Although, the embodiment shown in FIG. 6 comprises the buried dopingregion 501, as introduced in FIG. 5 , this feature is independent fromthe features introduced in FIG. 6 .

FIGS. 7 a-e show cross-sectional electron microscopy images and typicaldimensions of a substrate 10, 10′ at different stages of the method 100according to an embodiment.

FIG. 7 a shows a show cross-sectional view of a substrate 10 with themasking layer 16 after the etching 120. The deep trench structure 20comprises a depth 27 which is a vertical dimension from the main surfaceregion 12 into the substrate 10. The depth 27 may be in the range asdescribed in the context of FIG. 2 b . For example, the depth 27 may bearound 15 μm.

FIG. 7 b shows an enlarged view of the rectangle in FIG. 7 a . Accordingto the shown embodiment, the masking layer 16 comprises a pad layer 16-1and a hard mask layer 16-2, the pad layer 16-1 having a thickness 701.The thickness 701 of the pad layer 16-1 may be in a range as describedin the context of FIG. 2 a . For example, the pad layer thickness 701may be around 130 nm. The deep trench structure 20 may have a width 25which may be in the range as described in the context of FIG. 2 b . Forexample, the width may be around 370 nm.

FIG. 7 c shows a cross-sectional view of a thickened substrate 10′having the buried deep trench structure 50 after step 150. The burieddeep trench structure 50 comprises the deep trench portions 50-1, 50-2,50-3.

FIG. 7 d shows an enlarged view of the rectangle 710 in FIG. 7 c ,showing the deep trench portion 50-3 comprising a depth 27. The depth 27may be in the range as described in the context of FIG. 2 b . Forexample, the depth 27 may be around 13 μm.

FIG. 7 e shows an enlarged view of the center rectangle 720 in FIG. 7 c, showing the depth of bury 54 of the buried deep trench structure 50below the main surface region 12′ o. The depth of bury 54 may be in therange as described in the context of FIG. 2 e . For example, the depthof bury 54 may be around 2 μm.

FIG. 8 shows an example of a lateral distribution of dopants in thetrench doping region 60 of a sensor device manufactured according to anembodiment of the method 100. The plot shows a concentration of dopantsalong a lateral direction from a doped layer 32 into the thickenedsubstrate 10′. Other distributions can however be obtained as desired.

FIG. 9 shows schematic cross-sectional views (schematic snapshots) of asubstrate and elements of the sensor device at different stages of themanufacturing according to a further embodiment, which comprises anadditional step 132 of depositing 132 a trench coating layer 90 on asurface region 36 of the doped layer 32, wherein the selectivedepositing 130 of the doped layer 32 and the depositing 132 of thetrench coating layer 90 together provide the coated deep trenchstructure 30.

FIG. 9 shows the stages of the manufacturing process after the steps130, 132, 140 and 150. After step 130, the substrate 10, which mayoptionally comprise the buried doping region 501, still has the maskinglayer 16 and the deep trench structure is coated with the doped layer 32having the thickness 34 and the surface region 36.

The additional depositing step 132 follows the step 130 of depositingthe doped layer 32. The depositing 132 of the trench coating layer 90may for example be an epitaxy process. For example, the depositing 132may be a selective epitaxy process which is configured to deposit asemiconducting material primarily on the doped layer 32, such that themasking layer 16 may remain free of this material. The trench coatinglayer 90 may comprise a semiconductor material configured to reduce orblock the out-diffusion of boron. The trench coating layer 90 maycomprise an undoped semiconductor material, such as undoped silicon, butthe trench coating layer 90 may also comprise a low-doped semiconductormaterial with a doping concentration less than the doping concentrationof the doped layer 32. For example, the doping concentration of thetrench coating layer 90 may be smaller than the doping concentration ofthe substrate 10. For example, the doping concentration of the trenchcoating layer 90 may be lower than 10¹⁵ cm⁻³. The trench coating layer90 may have a thickness 38, which may be lower than 1 μm. Alternatively,the trench coating layer 90 may comprise an insulating material, forexample silicon nitride, for example in combination with the thickness38 of the trench coating layer 90 being below 100 nm.

The trench coating layer 90 may cover the surface region 36 of the dopedlayer 32. At least, the trench coating layer 90 covers a top surfaceregion 37 of the doped layer 32. For example, the top surface region 37of the doped layer 32 may be a surface region of the doped layer 32which extends vertically above the main surface region 12 of thesubstrate and which is adjacent to the masking layer 16.

The selective depositing 130 of the doped layer 32 and the depositing132 of the trench coating layer 90 together provide the coated deeptrench structure 30 which may comprise the dimensions and thefunctionality as described above. After the deposition 132 of the trenchcoating layer 90, the method 100 may be pursued with the removal 140 ofthe masking layer 16 and the deposition 150 of the semiconductor cappinglayer as described with respect to FIGS. 1-8 .

By covering at least the top surface region 37 of the doped layer 32,the extent of the contact region between the doped layer 32 and thecapping layer 52 may be reduced. In other words, the trench coatinglayer 90 is then configured to reduce the surface of the doped layer 32which will be in contact with the capping layer 52 once it is formed. Asa consequence, the amount of dopants that may diffuse from the dopedlayer 32 into the capping layer 52 during the depositing 150 of thecapping layer 52 or during the subsequent step of out-diffusing 160 ofdopants may be reduced. Reducing this diffusion may prevent the diffuseddopants from interfering with elements in or on the capping layer 52,such as circuitry 70, during an operation of the sensor device.

FIG. 10 shows schematic cross-sectional views (schematic snapshots) ofthe substrate 10 and elements of the sensor device after the steps 130,140 and 150 of the manufacturing according to a further embodiment ofthe method 100. Steps 130 and 140 correspond to the steps 130 and 140 asdescribed with respect to FIGS. 1-9 . Optionally, the method may alsocomprise the deposition 132 as described above. According to theembodiment shown in FIG. 10 , the step 150 of depositing the cappinglayer 52 comprises a step of depositing a first semiconductor cappinglayer 55 on the main surface region 12. Further, the depositing 150comprises a step of depositing a second semiconductor capping layer 57on the first semiconductor capping layer 55, the first semiconductorcapping layer 55 and the second semiconductor capping layer 57 formingtogether the capping layer 52. During this step, the depositing 155 ofthe first semiconductor capping layer 55 is performed at a lowertemperature than the depositing 157 of the second semiconductor cappinglayer 57.

The deposition of the first semiconductor capping layer 55 may be adeposition process like the deposition 150 of the capping layer 52described with respect to FIGS. 1-9 , but the deposition of the firstsemiconductor capping layer 55 may be performed at a lower temperatureor process temperature as the deposition process described with respectto the deposition 150 in the description of the FIGS. 1-9 . Thedeposition of the first semiconductor capping layer 55 closes the coateddeep trench structure 30 as described with respect to the deposition 150of the capping layer 52 in the description of the FIGS. 1-9 .

The deposition of the second semiconductor capping layer 57 may forexample be a growing of the second semiconductor capping layer 57 on topof the first semiconductor capping layer 55. The deposition of thesecond semiconductor capping layer 57 may be a deposition process likethe deposition 150 described with respect to the FIGS. 1-9 and thedeposition of the second semiconductor capping layer 57 may be performedat a temperature as described with respect to the deposition 150.

The temperature of the deposition of the first semiconductor cappinglayer 55 is for instance lower by more than 50° C. than the temperatureof deposition of the deposition of the second semiconductor cappinglayer 57. For instance, the temperature difference may be more than 100°C., or more than 200° C.

Depositing the first semiconductor capping layer 55 at a lowertemperature may help to reduce diffusion of dopants of the doped layer32 into the capping layer 52.

FIG. 11 shows schematic cross-sectional views (schematic snapshots) of asubstrate and elements of the sensor device at different stages of themanufacturing process according to an embodiment. Between the steps 120and 130, the embodiment comprises an additional step 122 of widening thedeep trench structure 20, the steps of etching 120 and widening 122together providing the deep trench structure 20.

The widening 122 of the deep trench structure 20 corresponds to aremoval of matter of the substrate 10 from the surface 22 of the deeptrench structure 20 over all or part of the height of the deep trenchstructure 20.

The widening 122 may be carried out using an isotropic etching process,for example a dry etch process. Alternatively, it may be carried outusing an anisotropic etch process, such as a wet etch process.

The widening 122 may laterally remove material of the substrate 10 froma surface region of the deep trench structure 20 located adjacent orvertically below the masking layer 16 for providing an undercut 29 ofthe deep trench structure 20 with respect to the masking layer 16. Inother words, in a region vertically below the masking layer 16, the deeptrench structure 20 may have a larger lateral dimension than therevealed areas 18 (c.f. FIGS. 2 a-b ) of the masking layer 16, theexcess of the lateral dimension of the deep trench structure regardingthe revealed areas 18 of the masking layer 16 defining the undercut 29.The undercut 29 may also be regarded as an overhang of the masking layer16 over the deep trench structure 20.

The dimension of the undercut 29 may be at least as large as thethickness 34 of the doped layer 32 which is deposited in the subsequentstep 130. The undercut 29 of the deep trench structure 20 leads to aconfiguration in which the masking layer 16 caps the top surface region37, as introduced with respect to FIG. 9 , of the doped layer 32 afterthe doped layer 32 has been deposited in the subsequent step 130.However, in this embodiment, the top surface region 37 does not extendbeyond the main surface region 12. In other words, the top surfaceregion 37 of the doped layer 32 may be arranged vertically below themasking layer 16.

This configuration helps prevent lateral contacts between the dopedlayer 32 and the capping layer 52, reducing diffusion of dopants fromthe doped layer 32 into the capping layer 52, e.g. during the deposition150 of the capping layer 52.

As indicated above, the steps of etching 120 and widening 122 togetherprovide the deep trench structure 20. Following step 122, the subsequentprocess steps may be performed in accordance to the embodiments of FIGS.1 to 9 .

The embodiments of FIG. 9 to FIG. 11 may be combined, whether two ofthem according to all possible combinations, or all three of them.

FIG. 12 shows a schematic cross-sectional view of a sensor device with aburied deep trench structure according to an embodiment. The sensordevice comprises the substrate 10′ having the sensing region 14′, thecapping layer 52, the buried deep trench structure 50 comprising thedoped layer 32, the trench doping region 60, and the electroniccircuitry 70 for the sensing region 14′ in the capping region 72vertically above the buried deep trench structure 50.

The sensor device provides the functionalities and advantages asdescribed with respect to the method 100 for manufacturing a sensordevice.

In the foregoing Detailed Description, it can be seen that variousfeatures are grouped together in examples for the purpose ofstreamlining the disclosure. This method of disclosure is not to beinterpreted as reflecting an intention that the claimed examples requiremore features than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive subject matter may lie in less thanall features of a single disclosed example. Thus, the following claimsare hereby incorporated into the Detailed Description, where each claimmay stand on its own as a separate example. While each claim may standon its own as a separate example, it is to be noted that, although adependent claim may refer in the claims to a specific combination withone or more other claims, other examples may also include a combinationof the dependent claim with the subject matter of each other dependentclaim or a combination of each feature with other dependent orindependent claims. Such combinations are proposed herein unless it isstated that a specific combination is not intended. Furthermore, it isintended to include also features of a claim to any other independentclaim even if this claim is not directly made dependent to theindependent claim.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present embodiments. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that theembodiments be limited only by the claims and the equivalents thereof.

What is claimed is:
 1. A method for manufacturing a sensor device with aburied deep trench structure, the method comprising: providing asemiconductor substrate having a sensing region which extends verticallybelow a main surface region of the semiconductor substrate into thesemiconductor substrate, wherein a masking layer is arranged on the mainsurface region of the semiconductor substrate; etching a deep trenchstructure into the semiconductor substrate through revealed areas of themasking layer such that the deep trench structure is arranged laterallyrelative to the sensing region and vertically from the main surfaceregion into the semiconductor substrate; selectively depositing byepitaxy a doped semiconductor layer on a surface region of the deeptrench structure to provide a coated deep trench structure; at leastpartially removing the masking layer to reveal the main surface regionof the semiconductor substrate; depositing a semiconductor capping layeron the main surface region of the semiconductor substrate, wherein thesemiconductor capping layer covers and closes the coated deep trenchstructure and forms together with the semiconductor substrate athickened semiconductor substrate having the buried deep trenchstructure; and out-diffusing dopants of the doped semiconductor layerinto the thickened semiconductor substrate, wherein the out-diffuseddopants provide a trench doping region that extends from the dopedsemiconductor layer into the thickened semiconductor substrate, whereindepositing the semiconductor capping layer comprises: depositing a firstsemiconductor capping layer on the main surface region of thesemiconductor substrate; and depositing a second semiconductor cappinglayer on the first semiconductor capping layer, wherein the firstsemiconductor capping layer and the second semiconductor capping layertogether form the semiconductor capping layer, and wherein thedepositing of the first semiconductor capping layer is performed at alower temperature than the depositing of the second semiconductorcapping layer.
 2. The method of claim 1, wherein the doped semiconductorlayer is deposited to have a doping concentration between 10¹⁶ and 10²⁰cm⁻³ and a thickness in a range between 1 nm and 100 nm.
 3. The methodof claim 1, further comprising: depositing a trench coating layer on asurface region of the doped semiconductor layer, wherein the selectivedepositing of the doped semiconductor layer and the depositing of thetrench coating layer together provide the coated deep trench structure.4. The method of claim 1, further comprising: widening the deep trenchstructure; wherein the etching of the deep trench structure and thewidening of the deep trench structure together provide the deep trenchstructure.
 5. The method of claim 1, further comprising: before thedepositing of the semiconductor capping layer, filling the coated deeptrench structure with a gas or with a dielectric material.
 6. The methodof claim 5, wherein the dielectric material filling the coated deeptrench structure is optically opaque for an optical radiation to bedetected in the sensing region.
 7. The method of claim 1, wherein duringthe etching of the deep trench structure, a plurality of deep trenchportions are etched into the semiconductor substrate to form the deeptrench structure, and wherein the deep trench portions are formed to atleast partially or completely laterally surround the sensing region inthe semiconductor substrate.
 8. The method of claim 1, wherein the deeptrench structure has a depth in a range between 2 μm and 50 μm and has awidth in a range between 50 nm and 2 μm.
 9. The method of claim 1,wherein the semiconductor substrate comprises a buried doping regionarranged vertically below the sensing region in the semiconductorsubstrate, wherein the sensing region and the buried doping region arearranged to have complimentary doping types, and wherein the deep trenchstructure extends vertically from the main surface region of thesemiconductor substrate into the buried doping region.
 10. The method ofclaim 1, further comprising arranging an electronic circuitry for thesensing region in a capping region of the thickened semiconductorsubstrate vertically above the buried deep trench structure.
 11. Themethod of claim 1, wherein the sensor device comprises optical operativesensing regions, and wherein the buried deep trench structure at leastpartially or completely laterally individually encloses separate ones ofthe optical operative sensing regions.
 12. The method of claim 1,wherein the trench doping region is arranged to provide, in an operativecondition of the sensor device, a defined electrical drift fielddistribution in sensing regions of the thickened semiconductorsubstrate.
 13. The method of claim 1, wherein with the semiconductorcapping layer in place, the coated deep trench structure is empty orfilled with gas.
 14. The method of claim 1, wherein with thesemiconductor capping layer in place, the coated deep trench structureis filled with a dielectric material.
 15. A method for manufacturing asensor device with a buried deep trench structure, the methodcomprising: providing a semiconductor substrate having a sensing regionwhich extends vertically below a main surface region of thesemiconductor substrate into the semiconductor substrate, wherein amasking layer is arranged on the main surface region of thesemiconductor substrate; etching a deep trench structure into thesemiconductor substrate through revealed areas of the masking layer suchthat the deep trench structure is arranged laterally relative to thesensing region and vertically from the main surface region into thesemiconductor substrate; selectively depositing by epitaxy a dopedsemiconductor layer on a surface region of the deep trench structure toprovide a coated deep trench structure; at least partially removing themasking layer to reveal the main surface region of the semiconductorsubstrate; depositing a semiconductor capping layer on the main surfaceregion of the semiconductor substrate, wherein the semiconductor cappinglayer covers and closes the coated deep trench structure and formstogether with the semiconductor substrate a thickened semiconductorsubstrate having the buried deep trench structure; and out-diffusingdopants of the doped semiconductor layer into the thickenedsemiconductor substrate, wherein the out-diffused dopants provide atrench doping region that extends from the doped semiconductor layerinto the thickened semiconductor substrate, wherein with thesemiconductor capping layer in place, the coated deep trench structureis empty or filled with gas.
 16. A method for manufacturing a sensordevice with a buried deep trench structure, the method comprising:providing a semiconductor substrate having a sensing region whichextends vertically below a main surface region of the semiconductorsubstrate into the semiconductor substrate, wherein a masking layer isarranged on the main surface region of the semiconductor substrate;etching a deep trench structure into the semiconductor substrate throughrevealed areas of the masking layer such that the deep trench structureis arranged laterally relative to the sensing region and vertically fromthe main surface region into the semiconductor substrate; selectivelydepositing by epitaxy a doped semiconductor layer on a surface region ofthe deep trench structure to provide a coated deep trench structure; atleast partially removing the masking layer to reveal the main surfaceregion of the semiconductor substrate; depositing a semiconductorcapping layer on the main surface region of the semiconductor substrate,wherein the semiconductor capping layer covers and closes the coateddeep trench structure and forms together with the semiconductorsubstrate a thickened semiconductor substrate having the buried deeptrench structure; and out-diffusing dopants of the doped semiconductorlayer into the thickened semiconductor substrate, wherein theout-diffused dopants provide a trench doping region that extends fromthe doped semiconductor layer into the thickened semiconductorsubstrate, wherein with the semiconductor capping layer in place, thecoated deep trench structure is filled with only a dielectric material.